material-components_material-components-ios/components/Cards/examples/EditReorderCollectionViewController.swift

/*
 Copyright 2018-present the Material Components for iOS authors. All Rights Reserved.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

 http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */

import UIKit

enum ToggleMode: Int {
  case edit = 1, reorder
}

class EditReorderCollectionViewController: UIViewController,
  UICollectionViewDelegate,
  UICollectionViewDataSource,
  UICollectionViewDelegateFlowLayout {

  let collectionView = UICollectionView(frame: .zero,
                                        collectionViewLayout: UICollectionViewFlowLayout())
  var dataSource = [(Int, Bool)]()
  var longPressGesture: UILongPressGestureRecognizer!
  var toggle = ToggleMode.reorder
  var toggleButton: UIButton!
  
  override func viewDidLoad() {
    super.viewDidLoad()

    collectionView.frame = view.bounds
    collectionView.dataSource = self
    collectionView.delegate = self
    collectionView.backgroundColor = UIColor(white: 0.9, alpha: 1)
    collectionView.alwaysBounceVertical = true;
    collectionView.register(MDCCardCollectionCell.self, forCellWithReuseIdentifier: "Cell")
    collectionView.translatesAutoresizingMaskIntoConstraints = false
    collectionView.allowsMultipleSelection = true
    view.addSubview(collectionView)

    navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Reorder",
                                                        style: .plain,
                                                        target: self,
                                                        action: #selector(toggleModes))

    if #available(iOS 9.0, *) {
      longPressGesture = UILongPressGestureRecognizer(target: self,
                                                      action: #selector(handleReordering(gesture:)))
      longPressGesture.cancelsTouchesInView = false
      collectionView.addGestureRecognizer(longPressGesture)
    }

    for i in 0..<20 {
      dataSource.append((i, false))
    }

    #if swift(>=3.2)
      if #available(iOS 11, *) {
        let guide = view.safeAreaLayoutGuide
        NSLayoutConstraint.activate([
          collectionView.leftAnchor.constraint(equalTo: guide.leftAnchor),
          collectionView.rightAnchor.constraint(equalTo: guide.rightAnchor),
          collectionView.topAnchor.constraint(equalTo: view.topAnchor),
          collectionView.bottomAnchor.constraint(equalTo: guide.bottomAnchor)])
        collectionView.contentInsetAdjustmentBehavior = .always
      } else {
        preiOS11Constraints()
      }
    #else
      preiOS11Constraints()
    #endif

  }

  func preiOS11Constraints() {
    self.view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|[view]|",
                                                                 options: [],
                                                                 metrics: nil,
                                                                 views: ["view": collectionView]));
    self.view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|[view]|",
                                                                 options: [],
                                                                 metrics: nil,
                                                                 views: ["view": collectionView]));
  }

  func toggleModes() {
    if toggle == .edit {
      toggle = .reorder
      navigationItem.rightBarButtonItem?.title = "Reorder"
    } else if toggle == .reorder {
      toggle = .edit
      navigationItem.rightBarButtonItem?.title = "Edit"
    }
    collectionView.reloadData()
  }

  func collectionView(_ collectionView: UICollectionView,
                      cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell",
                                                  for: indexPath) as! MDCCardCollectionCell
    cell.backgroundColor = .white
    cell.isSelectable = (toggle == .edit)
    return cell
  }

  func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    if toggle == .edit {
      dataSource[indexPath.item].1 = !dataSource[indexPath.item].1
    }
  }

  func numberOfSections(in collectionView: UICollectionView) -> Int {
    return 1
  }

  func collectionView(_ collectionView: UICollectionView,
                      numberOfItemsInSection section: Int) -> Int {
    return dataSource.count
  }

  func collectionView(_ collectionView: UICollectionView,
                      moveItemAt sourceIndexPath: IndexPath,
                      to destinationIndexPath: IndexPath) {
  }

  func collectionView(_ collectionView: UICollectionView,
                      layout collectionViewLayout: UICollectionViewLayout,
                      sizeForItemAt indexPath: IndexPath) -> CGSize {
    let cardSize = (collectionView.bounds.size.width / 3) - 12
    return CGSize(width: cardSize, height: cardSize)
  }

  func collectionView(_ collectionView: UICollectionView,
                      layout collectionViewLayout: UICollectionViewLayout,
                      insetForSectionAt section: Int) -> UIEdgeInsets {
    return UIEdgeInsets(top: 8, left: 8, bottom: 8, right: 8)
  }

  func collectionView(_ collectionView: UICollectionView,
                      layout collectionViewLayout: UICollectionViewLayout,
                      minimumLineSpacingForSectionAt section: Int) -> CGFloat {
    return 8
  }

  func collectionView(_ collectionView: UICollectionView,
                      layout collectionViewLayout: UICollectionViewLayout,
                      minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
    return 8
  }

  func collectionView(_ collectionView: UICollectionView,
                      canMoveItemAt indexPath: IndexPath) -> Bool {
    return toggle == .reorder
  }

  @available(iOS 9.0, *)
  @objc func handleReordering(gesture: UILongPressGestureRecognizer) {
    if toggle == .reorder {
      switch(gesture.state) {
      case .began:
        guard let selectedIndexPath = collectionView.indexPathForItem(at:
          gesture.location(in: collectionView)) else {
          break
        }
        collectionView.beginInteractiveMovementForItem(at: selectedIndexPath)
      case .changed:
        collectionView.updateInteractiveMovementTargetPosition(gesture.location(in: gesture.view!))
      case .ended:
        collectionView.endInteractiveMovement()
      default:
        collectionView.cancelInteractiveMovement()
      }
    }
  }

}

extension EditReorderCollectionViewController {
  @objc class func catalogBreadcrumbs() -> [String] {
    return ["Cards", "Edit/Reorder (Swift)"]
  }

  @objc class func catalogIsPresentable() -> Bool {
    return true
  }

  @objc class func catalogIsDebug() -> Bool {
    return false
  }

  @objc class func catalogIsPrimaryExample() -> Bool {
    return true
  }
}